Na­ture or nur­ture for in­let?

He re­counted how a young sailor smashed his front teeth when he hit the sand­bar near Browns Bay – a par­tic­u­larly tough one to nav­i­gate.

He told Kapi-mana News last week that while the DHI re­port was still to be dis­cussed by the PBC com­mit­tee, they had been in favour of limited dredg­ing of this sand­bar.

‘‘It’s a nar­row chan­nel and from a safety point of view, we need to be Dredg­ing Pau­ata­hanui In­let has been de­scribed as ‘‘ lit­er­ally throw­ing $5 mil­lion into a hole’’ but at least one or­gan­i­sa­tion does not be­lieve the op­tion should be dis­counted.

Porirua City Coun­cil and Greater Welling­ton Re­gional Coun­cil com­mis­sioned re­search group DHI Water and En­vi­ron­ment to in­ves­ti­gate whether lo­calised dredg­ing in the in­let would im­prove the flush­ing of the es­tu­ary’s mud and sand. Its re­port – avail­able on the PCC web­site – found ti­dal speeds would have to in­crease con­sid­er­ably to en­able sed­i­ment and sand to be flushed out and that dredg­ing would not as­sist this.

This is also the same sce­nario for the Onepoto arm of the har­bour, ac­cord­ing to other ad­vice PCC re­ceived.

The DHI re­port fol­lows a hear­ing held late last year on the Porirua Har­bour and Catch­ment Strat­egy and Ac­tion Plan.

Four sub­mit­ters pro­moted dredg­ing the har­bour.

Pare­mata Boat­ing Club ( PBC) com­modore Paul Pet­tit told the hear­ing that ac­cess and nav­i­ga­tion were key to mem­bers en­joy­ing the

To dredge or not? The is­sue has been put to bed in politi­cians’ minds but mem­bers of the sail­ing com­mu­nity want the door left open. able to get res­cue boats in there quickly some­times. Per­son­ally, I think clos­ing the door on it [dredg­ing] now de­pends on what the in­let’s go­ing to be like in the fu­ture. If you can stop the sed­i­men­ta­tion buildup, cool, but if in 30 years time it hasn’t been stopped, do you re­visit dredg­ing?’’

The DHI re­port gives two op­tions for con­trol­ling sed­i­men­ta­tion – dredg­ing, which will only ‘‘main­tain the har­bour’’, or con­trol­ling what comes into the in­let from the catch­ments.

‘‘ How­ever, it’s cur­rently hap­pen­ing much faster than it should and must be re­duced if we are to suc­ceed in re­vi­tal­is­ing the har­bour.’’

DHI pre­dicted the chan­nels were likely to fill with sand ‘‘ rea­son­ably quickly’’ even if dredg­ing was car­ried out. One, off the end of Seav­iew Rd, would cost $800,000 to dredge and $4m to dis­pose of the sand.

Porirua Mayor Nick Leggett is un­equiv­o­cal on the is­sue.

‘‘ It would be lit­er­ally like throw­ing $ 5m into a hole that would be in­ef­fec­tive and even­tu­ally re­filled with sand.

‘‘Peo­ple need to un­der­stand that this is not Lake Taupo – it’s a ti­dal es­tu­ary that’s con­stantly mov­ing, and sand­banks and mud­flats are nor­mal. This [DHI] re­port firmly shuts the door on lo­calised dredg­ing.’’